The present invention relates to a method of manufacturing a solar battery, more particularly to a method of manufacturing a solar battery constituted by electrically connecting a plurality of cells to one another by connection members referred to as tabs or tab lead wires.
In recent years, from a global environment protection problem such as global warming, expectations for clean energy have grown, and a solar battery which directly converts solar energy (sunlight) into electric energy has received attention as a clean energy source. For example, the solar battery includes a plurality of photoelectric conversion cells, and tabs each constituted of a copper foil is soldered to these adjacent cells to electrically connect them to one another, thereby constituting a string. This tab is used as a lead wire which connects a plurality of cells in series or as an output terminal (see Japanese Patent Application Laid-Open No. 2003-168811).
In a general method of manufacturing such a solar battery string 100, as shown in FIG. 9, first a plurality of cells 12 are prepared (first step). Moreover, after applying a liquefied flux warmed at a predetermined temperature to portions (shown dotted lines) of the surfaces of the plurality of cells 12 where tabs 14 are to be soldered (second step), the tabs 14 are disposed on the top of the cell 12 and the undersurface of the adjacent cell 12 (third step). Next, the tabs 14 are pressed onto the cells 12 from above so as to prevent the arranged tabs 14 from being raised, and the tabs 14 are soldered (fourth step).
When such tabs 14 are soldered onto the surfaces of the cells 12, organic matters and the like mixed with the flux are attached to the cells 12. If these organic matters and the flux remain on the surfaces of the cells 12, an energy conversion efficiency of the solar battery deteriorates. Therefore, heretofore, after soldering the tabs 14 onto the cells 12, a cleaning step of cleaning the cells 12 has been performed to clean and remove residues such as the flux and the organic matters from the surfaces of the cells 12 with warm water, chemicals, steam or the like.
Moreover, the string 100 constituted of the plurality of cells 12 cleaned in this manner is disposed between a protective sheet or light transmitting glass on the backside and light transmitting glass on the surface, and sealed with a filler (EVA or the like), whereby the solar battery is manufactured. There is also a case where residues such as the flux and the organic matters on the surfaces of the cells 12 are disposed between pieces of glass or between the glass and the sheet as they are without being cleaned in a sealed manner.
However, the operation of cleaning and removing residues such as the flux and the organic matters on the cell surfaces with the warm water, chemical, steam or the like after soldering the tabs causes an increase of steps of manufacturing the solar battery. Therefore, there is a problem that a cost increase of the solar battery is caused.
Moreover, in a case where after soldering the tabs, residues such as the flux and the organic matters on the cell surfaces are disposed between the pieces of glass or between the glass and the sheet without being cleaned in the sealed manner, even when residues such as the flux and the organic matters remain on the cell surfaces, they cannot be removed. Especially in a case where residues such as the organic matters and the flux on the cell surfaces are gasified by heating in a step of forming a module or the like, and remain as a large number of bubbles, sunlight striking on the cell surfaces is irregularly reflected, or the sunlight is intercepted. Therefore, there is a problem that a drop of the energy conversion efficiency of the solar battery is incurred.